1. Field of the Invention
The invention relates to a thrust bearing (axial bearing), in particular to a turbo charger, having an essentially disc shaped bearing body with a central through opening for a shaft, having at least one bearing surface surrounding the through opening for a collar which is placed on the shaft and also having at least one oil supply channel, which leads from a radially outer region of the bearing body to the through opening. The invention further relates to a turbo charger with a thrust bearing of such type.
2. Related Art of the Invention
The shaft of a turbo charger, for example, rotates with a high speed and therefore must be supported both axially as well as radially, since, depending on the load condition, axial forces are generated either through the compressor wheel or the turbine wheel. A thrust bearing of the type mentioned at the outset and which is fixed firmly in the shaft housing is used for absorbing such axial forces. The shaft is supported at each side on the thrust bearing by a collar which is fixed firmly on the shaft and is separated from the thrust bearing through a thin lubricating film. A recess is provided in a radially outer zone of the bearing body with the purpose of supplying lubricating oil to the bearing surfaces. This recess is provided with oil under pressure by way of oil supply channels in the bearing housing of the turbo charger. It is, however, necessary that the lubricating oil in this case is first led radially inwards to the shaft, from where it can reach the bearing surfaces over the oil supply channels. For this purpose the known thrust bearing has several radial bores which lead from the recess to the through opening. The disadvantage of this construction form is that, because of the flat design of the bearing body, it is not possible to drill directly from the recess to the through opening. Instead, it is necessary to radially drill through the complete bearing body, starting from the outer edge. Apart from the desired channels between the recess and the through opening, additional channels between the recess and the outer edge of the bearing body are formed. These additional channels need to be closed again, in order to prevent any escape of lubricating oil through these channels. Drilling these additional channels and again closing them is a very elaborate process, contributing heavily towards the total cost of the thrust bearing. Additionally, the is a risk that, in case of any deficiency in closing a channel, it could become free later, which would cause a collapse of the lubricating oil pressure and consequently damage to the bearing.